Return a String from collapsed_doc_value, not an Option

This has almost no effect in practice, since most places were using `unwrap_or_default`,
and the rest were doing checks that *should* have been checking for an empty string.

The only change in behavior is that the JSON backend no longer distinguishes
"undocumented" and "documented with the empty string". This doesn't seem like a particularly useful distinction,
but I can add it back for that code only if you think it's important.

Author: jyn514

src/librustdoc/clean/types.rs

@@ -468,7 +468,7 @@ impl Item {
 
     /// Finds all `doc` attributes as NameValues and returns their corresponding values, joined
     /// with newlines.
-    crate fn collapsed_doc_value(&self) -> Option<String> {
+    crate fn collapsed_doc_value(&self) -> String {
         self.attrs.collapsed_doc_value()
     }
 
@@ -956,16 +956,6 @@ fn add_doc_fragment(out: &mut String, frag: &DocFragment) {
     }
 }
 
-/// Collapse a collection of [`DocFragment`]s into one string,
-/// handling indentation and newlines as needed.
-crate fn collapse_doc_fragments(doc_strings: &[DocFragment]) -> String {
-    let mut acc = String::new();
-    for frag in doc_strings {
-        add_doc_fragment(&mut acc, frag);
-    }
-    acc
-}
-
 /// A link that has not yet been rendered.
 ///
 /// This link will be turned into a rendered link by [`Item::links`].
@@ -1104,12 +1094,15 @@ impl Attributes {
 
     /// Finds all `doc` attributes as NameValues and returns their corresponding values, joined
     /// with newlines.
-    crate fn collapsed_doc_value(&self) -> Option<String> {
-        if self.doc_strings.is_empty() {
-            None
-        } else {
-            Some(collapse_doc_fragments(&self.doc_strings))
-        }
+    ///
+    /// Unlike `doc_value`, this does not stop processing lines when switching between `#[doc]` and
+    /// sugared syntax.
+    crate fn collapsed_doc_value(&self) -> String {
+        let mut acc = String::new();
+        for frag in &self.doc_strings {
+            add_doc_fragment(&mut acc, frag);
+        }
+        acc
     }
 
     crate fn get_doc_aliases(&self) -> Box<[Symbol]> {

src/librustdoc/doctest.rs

@@ -1123,17 +1123,17 @@ impl<'a, 'hir, 'tcx> HirCollector<'a, 'hir, 'tcx> {
         }
 
         attrs.unindent_doc_comments();
-        // The collapse-docs pass won't combine sugared/raw doc attributes, or included files with
-        // anything else, this will combine them for us.
-        if let Some(doc) = attrs.collapsed_doc_value() {
+        // `doc_value()` doesn't combine sugared/raw doc attributes, this will combine them for us.
+        let docs = attrs.collapsed_doc_value();
+        if !docs.is_empty() {
             // Use the outermost invocation, so that doctest names come from where the docs were written.
             let span = ast_attrs
                 .span()
                 .map(|span| span.ctxt().outer_expn().expansion_cause().unwrap_or(span))
                 .unwrap_or(DUMMY_SP);
             self.collector.set_position(span);
             markdown::find_testable_code(
-                &doc,
+                &docs,
                 self.collector,
                 self.codes,
                 self.collector.enable_per_target_ignores,

src/librustdoc/html/render/mod.rs

@@ -567,19 +567,21 @@ fn document_full_inner(
     is_collapsible: bool,
     heading_offset: HeadingOffset,
 ) {
-    if let Some(s) = item.collapsed_doc_value() {
-        debug!("Doc block: =====\n{}\n=====", s);
+    // NOTE: "collapsed" here is unrelated to `is_collapsible`, it just combines `#[doc]` and sugared attributes
+    let docs = item.collapsed_doc_value();
+    if !docs.is_empty() {
+        debug!("Doc block: =====\n{}\n=====", docs);
         if is_collapsible {
             w.write_str(
                 "<details class=\"rustdoc-toggle top-doc\" open>\
                 <summary class=\"hideme\">\
                      <span>Expand description</span>\
                 </summary>",
             );
-            render_markdown(w, cx, &s, item.links(cx), heading_offset);
+            render_markdown(w, cx, &docs, item.links(cx), heading_offset);
             w.write_str("</details>");
         } else {
-            render_markdown(w, cx, &s, item.links(cx), heading_offset);
+            render_markdown(w, cx, &docs, item.links(cx), heading_offset);
         }
     }
 
@@ -1612,7 +1614,8 @@ fn render_impl(
             write!(w, "</summary>")
         }
 
-        if let Some(ref dox) = i.impl_item.collapsed_doc_value() {
+        let dox = i.impl_item.collapsed_doc_value();
+        if !dox.is_empty() {
             let mut ids = cx.id_map.borrow_mut();
             write!(
                 w,

src/librustdoc/passes/bare_urls.rs

@@ -68,7 +68,7 @@ impl<'a, 'tcx> DocVisitor for BareUrlsLinter<'a, 'tcx> {
                 return;
             }
         };
-        let dox = item.attrs.collapsed_doc_value().unwrap_or_default();
+        let dox = item.attrs.collapsed_doc_value();
         if !dox.is_empty() {
             let report_diag = |cx: &DocContext<'_>, msg: &str, url: &str, range: Range<usize>| {
                 let sp = super::source_span_for_markdown_range(cx.tcx, &dox, &range, &item.attrs)

src/librustdoc/passes/calculate_doc_coverage.rs

@@ -208,7 +208,7 @@ impl<'a, 'b> DocVisitor for CoverageCalculator<'a, 'b> {
                 let mut tests = Tests { found_tests: 0 };
 
                 find_testable_code(
-                    &i.attrs.collapsed_doc_value().unwrap_or_default(),
+                    &i.attrs.collapsed_doc_value(),
                     &mut tests,
                     ErrorCodes::No,
                     false,

src/librustdoc/passes/check_code_block_syntax.rs

@@ -145,7 +145,8 @@ impl<'a, 'tcx> SyntaxChecker<'a, 'tcx> {
 
 impl<'a, 'tcx> DocVisitor for SyntaxChecker<'a, 'tcx> {
     fn visit_item(&mut self, item: &clean::Item) {
-        if let Some(dox) = &item.attrs.collapsed_doc_value() {
+        let dox = &item.attrs.collapsed_doc_value();
+        if !dox.is_empty() {
             let sp = item.attr_span(self.cx.tcx);
             let extra = crate::html::markdown::ExtraInfo::new_did(
                 self.cx.tcx,

src/librustdoc/passes/check_doc_test_visibility.rs

@@ -35,9 +35,7 @@ crate fn check_doc_test_visibility(krate: Crate, cx: &mut DocContext<'_>) -> Cra
 
 impl<'a, 'tcx> DocVisitor for DocTestVisibilityLinter<'a, 'tcx> {
     fn visit_item(&mut self, item: &Item) {
-        let dox = item.attrs.collapsed_doc_value().unwrap_or_else(String::new);
-
-        look_for_tests(self.cx, &dox, &item);
+        look_for_tests(self.cx, &item.attrs.collapsed_doc_value(), &item);
 
         self.visit_item_recur(item)
     }

src/librustdoc/passes/html_tags.rs

@@ -176,7 +176,7 @@ impl<'a, 'tcx> DocVisitor for InvalidHtmlTagsLinter<'a, 'tcx> {
                 return;
             }
         };
-        let dox = item.attrs.collapsed_doc_value().unwrap_or_default();
+        let dox = item.attrs.collapsed_doc_value();
         if !dox.is_empty() {
             let report_diag = |msg: &str, range: &Range<usize>| {
                 let sp = match super::source_span_for_markdown_range(tcx, &dox, range, &item.attrs)

src/librustdoc/passes/petrochenkov-suggestions.txt

@@ -0,0 +1,3 @@
+- use rustc's map instead of separate traits in scope
+- have a map from def id + link index to resolved DefId
+- need to have all 3 namespaces in case the link doesn't resolve

src/rustdoc-json-types/lib.rs

@@ -68,9 +68,8 @@ pub struct Item {
     /// By default all documented items are public, but you can tell rustdoc to output private items
     /// so this field is needed to differentiate.
     pub visibility: Visibility,
-    /// The full markdown docstring of this item. Absent if there is no documentation at all,
-    /// Some("") if there is some documentation but it is empty (EG `#[doc = ""]`).
-    pub docs: Option<String>,
+    /// The full markdown docstring of this item.
+    pub docs: String,
     /// This mapping resolves [intra-doc links](https://github.com/rust-lang/rfcs/blob/master/text/1946-intra-rustdoc-links.md) from the docstring to their IDs
     pub links: HashMap<String, Id>,
     /// Stringified versions of the attributes on this item (e.g. `"#[inline]"`)
@@ -511,7 +510,7 @@ pub struct Static {
 }
 
 /// rustdoc format-version.
-pub const FORMAT_VERSION: u32 = 9;
+pub const FORMAT_VERSION: u32 = 10;
 
 #[cfg(test)]
 mod tests;